The present invention concerns a memory-storage device of a coherent image in a multimode optical cavity.
The memory-storage of optical data assumes various forms and covers numerous fields of application: these include the recording of bidimensional or trimensional objects. Photography is the first form and, furthermore, essential form of optical storage, but lasers have encouraged the development of new processes applicable especially to audiovisual and data-processing fields. However, if research is widespread, present applications are limited. Two applications appear, indeed, to represent the possibilities offered by optical storage: holographic storage and the storage of television images on "video records".
The field of the invention is that of storage and subsequent processing, of coherent images. But contrary to the two applications mentioned above, this invention is directed toward the dynamic recording of coherent images.
Another possibility is envisaged in French Patent application filed Feb. 27, 1981 under No. 81 03989 that describes a device allowing the circulation in an optical guide, of a radiating energy impulse issuing from a coherent source at the propagation. The impulse is regenerated at a constant level. It is also possible, according to the device, to envisage an amplification of an incident energy radiating impulse by transferring the energy of a pumping beam towards the signal. This device thus ensures the circulation of a radiating energy impulse in a fiber while maintaining the level of the signal whatever the number of turns achieved. But in this case, it only involves an impulse, the amplitude of which is conserved while being propagated in a monomode wave guide. This device, indeed, does not allow the preservation of a wave front of any given form. This is the purpose proposed by the device according to the present invention. Indeed, the device according to the invention comprises a multimode optical cavity in which a stable oscillation of the coherent image is sustained.